[Effects of PEG additives on structure and performance of blend membranes]

Polysulfone(PSf) /polymer A blend membranes are fabricated by phase inversion process from casting solution of PSf, polymer A, DMAc, and polyethylene glycol (PEG). The resulting membranes prepared by changing the molecular weight of PEG additives are characterized by scanning electron microscope observation, measurement of water flux and trypsin retention. Experiments of water flux show that water fluxes have non-liner relationship with PEG molecular weight. The water flux of the membrane prepared from the PSf/A/PEG-4000/DMAc casting solution was 115.2mL x (cm2 x h)-1, six time as much as membrane without PEG-0. The PEG as a non-solvent changed thermodynamic properties in polymer solution, promoting phase demixing of casting solution; otherwise, it increased solution viscosity, delaying phase demixing. The two different effects work simultaneously, influencing structure and performance of the membranes.